The satellite broadcasting signals which use the microwave band includes linearly polarized waves and circularly polarized waves, and the circularly polarized waves include clockwise circularly polarized waves and counterclockwise circularly polarized waves.
Further, a rectangular microstrip patch is used as an effective means for receiving the satellite broadcasts of clockwise and counterclockwise circularly polarized waves. The currently existing circularly polarized wave signal pickup device using the conventional rectangular microstrip patch is illustrated in FIG. 1. As shown in this drawing, input probes 11 and 12 are installed on two edges of a rectangular microstrip patch 10, and the feeding lines of input probes 11 and 12 are connected to hybrid coupler 13, so that clockwise and clockwiseclockwise circularly polarized wave signals should be outputted through output ports 14 and 15 of the hybrid coupler 13.
Output port 14 outputs signals received by input probe 11, and signals received by input probe 12 which is phase-delayed by .lambda..sub.g /4, i.e., 90.degree.. Output port 15 outputs signals received by input probe 12 and signals received by input probe 11 which is phase-delayed by .lambda..sub.g /4, i.e., 90.degree.. Therefore, outputs ports 14 and 15 give circularly polarized waves (clockwise circularly polarized waves and counterclockwise circularly polarized waves) of mutually opposite phases.
In this conventional clockwise and counterclockwise circularly polarized wave receiving apparatus, the two circularly polarized wave signals are separated by means of only the hybrid coupler 13. Therefore, a part of the signals of output port 14 is leaked to output port 15, and a part of the signals of output port 15 is leaked to output port 14, with the result that the receiving efficiency is lowered. Further, due to the reflections of the signals leaked from the other output port, the isolation characteristics are deteriorated.